Two girls, aged 12 and 5, died when this bus came to grief while trying to ford a swollen river on the island of Savai'i.

The wife of the New Zealand Breakers' coach has described the "horrible" scenes after a bus carrying children and elderly people was swept away while attempting to cross a river during a flash flood in Samoa.

Christy Vickerman, husband Dean and other relatives were in another bus travelling back from a family reunion in the village of Tufutafoe on the island of Savai'i on Saturday when the disaster, which claimed the lives of two girls, unfolded in front of them.

"Everyone was freaking out," Mrs Vickerman said. "My sister got off the bus and went and helped a woman who had a toddler with a broken arm. The toddler was in quite a bit of shock.

"It was quite chaotic. The bus that went in was full and you couldn't tell how many people you were trying to save.

"A lot of people were exhausted. They couldn't even move their legs to stand, they were that exhausted. There were lots of cuts and bruises, people with their clothes ripped off by the force of the water.

It was quite horrible."

One of two Australian volunteer workers who was on the bus when it flipped thought it had been hit by a tsunami, Mrs Vickerman said.

Dean Vickerman, an Australian who has taken over as head coach of the champion Breakers basketball team, paid tribute to the bravery of his brothers-in-law in helping rescue passengers thrown into the torrent.

Cass Watson, a New Zealander who lives in Sydney, was the first person to wade in, Vickerman said. His other brother-in-law, Alan Silver, was close behind him.

"They were outstanding," Vickerman said. "Cass was the first one in there. He didn't hesitate at all. That certainly drove us to push a little further than we might have."

The bus driver's attempt to cross the swollen river was crazy, he said.

People from a nearby village were on the road warning motorists of the danger. The bus the Vickermans were on had pulled over to wait for the water to recede; however, the bus behind them pulled out and drove straight into the water.

"We certainly weren't going to try it," Vickerman said. "It was crazy. It got halfway across and just got washed down. I didn't quite see what happened but from all reports it flipped and the roof came off. It landed on some rocks and everybody was thrown out.

"It was just so fortunate that the roof came off and it landed up the right way.

"[We] jumped straight out of the bus and bowled down to see what we could do. We were just trying to drag as many people out as we could. The current was so strong.

"We started trying to pull people back against the current and you just couldn't move. You just had to grab people, get dragged out a bit then go sideways and get back to the shore."

Vickerman admitted he feared for his safety during the rescue.

"As you jump into the water there is that kind of thing in your mind about not being that guy who rescues someone else but loses their own life.

"But once you got into it and worked out the current you started to feel like the worst thing that could happen was that you'd get dragged out a little bit further."

It wasn't until they took a woman to hospital that the Vickermans learned that two girls, aged 12 and 5, had drowned.

"We had 10 kids on our bus," Vickerman said. "That was the scariest thing, learning two kids lost their lives."

Samoan media have reported the bus was trying to connect with a ferry sailing and was overloaded.